Two weekends ago I migrated our file storage, print services, logon scripts and domain security from Novell 5.1 to Windows NT for domain, Kixtart for the logon script and Win Server 2003 for the file and print services.
My first impressions of Win Server 2003 are favorable even compared to Server 2000. So far it runs pretty well, is fast, stable and has some really nice features.
One great feature if you are using Server 2003 for file services is the shadow copy feature. It makes a copy of the shares on a volume at a specific interval that you set up. This way you can recover a file or folder using any of the available show copies. Novell does a similar thing but only allows you to recover from deleted files. Shadow copy allows you to quickly recover from any issue with a file or folder, barring complete array failure. So if you accidently write over a file, no problem. Erase a file, no problem. Corrupt a file, no problem.
So far that's the major feature that I've found to be useful that is new in 2003.
There are also some nice tweaks to security and the interface, but I will get into those at a later time.